Rules for Multi value compression

Database
Enthusiast

Rules for Multi value compression

Can anyone help me on the below questions..

1. Is MVC allowed on primary index ?

2. Having MVC on too many columns will create problem ?

3.Is appliying compression on truncate and load tables are not ideal ?

4.Can we apply MVC on derived columns ?

2 REPLIES
Enthusiast

Re: Rules for Multi value compression

1. Is MVC allowed on primary index ? - No this is not possible.
 2. Having MVC on too many columns will create problem ? - No, the more columns you have compression on, the more savings you would get.
 3.Is appliying compression on truncate and load tables are not ideal ? - Why would you use compression on truncate and load tables. They would typically be stage tables. But, you can do it.
 4.Can we apply MVC on derived columns ? - I also need to test this.

--samir
Teradata Employee

Re: Rules for Multi value compression

1. no MVC on PIs

2. Can have MVC on as many columns as desired, no such thing as too many columns. If there is a very large number of very large values, it is possible to exceed the total space limit but it is unlikely.

3. Compression on trunc/load tables is fine. It costs very little to do MVC compression and it saves on IO for writing the data so it probably is a win for the load process and then is certainly a win for the accesses to the table.

4. What is meant by "derived column"?